Study of Some Lakes in the North-Eastern Romanian Plain Using the Coherence Image of the Tandem Pair (ERS-1 and ERS-2)


In radar SAR interferometry (InSAR/DinSAR), a Tandem pair (ERS-1/2) is used for the realization of a DEM or the detection of deformations of a major event (e.g. earthquake) occurring between two acquisitions. The advantage of the Tandem pair is the time interval of 24 hours between the two captures. Generally, there is no temporal decorrelation considering the small difference in time between the acquisitions, which results in a good coherence. The coherence image is used indirectly in radar SAR interferometry as an indicator of the levels of confidence of the interferograms. It can be used in a direct way to identify and delimit the various movement zones which disturb the phase of the radar wave. The objective of this work is to show the utility and the effectiveness of the coherence image in the cartography of lakes and vegetation in a region at the Curvature of the Romanian Carpathians1. Between the two acquisitions dates of May 28 and 29, 1995, there was no geological process involving displacements in direction of the radar. This pair represents the only one among the other pairs which gave a good coherence for the whole scene. In the flat part, one notes a good coherence except for the lakes. They are well represented by very dark colours with zero coherence. In the part of high altitude, especially where there is vegetation, a bad coherence can be clearly seen. Using this image (coherence), one could distinguish the parts with vegetation in great movements due to the effects of the wind, therefore characterised by great heights. The coherence image thus makes it possible to delimit two natural elements in this area, the lakes and the vegetation. The lakes are well delimited, in particular when they are full as in the rain seasons. To show this utility and this effectiveness of the coherence image, we measured the surfaces and dimensions of the lakes based on the Tandem pair and to make a comparison with the existing data and to interpret the results obtained. The three lakes, located in the plain to the East and North-East of the Buza;u town, clearly appear in the coherence image.

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Hachemi, K. , Jurchescu, M. , Grecu, F. , Ozer, A. and Visan, M. (2014) Study of Some Lakes in the North-Eastern Romanian Plain Using the Coherence Image of the Tandem Pair (ERS-1 and ERS-2). Advances in Remote Sensing, 3, 23-32. doi: 10.4236/ars.2014.31003.

Conflicts of Interest

The authors declare no conflicts of interest.


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